In recent years, personal cooling technologies have been developed to provide local environmental control to ensure the user remains thermally comfortable when in extreme environmental conditions such as those faced by athletes, the military, or EMS personnel. However, there remains a distinct lack of such technologies for everyday use by the average end user who spends the majority of the time in a sedentary state. This is especially important for indoor environments where incorporation of such technologies can offset energy consumed by HVAC systems for cooling while maintaining sufficient levels of thermal comfort. For instance, recent studies have shown that in the United States alone, residential and commercial buildings consume nearly 41% of total energy use each year with 37% of that energy devoted solely to heating and cooling, according to the 2011 Buildings Energy Data Book from the U.S. Department of Energy—Energy Efficiency & Renewable Energy Department (2011), and an article by Perez-Lombard, L.; Ortiz, J.; Pout, C.: A Review on Buildings Energy Consumption Information, Energy Build, 2008, 40, 394-398. To reduce energy usage, buildings have incorporated more renewable energy sources such as solar power, implemented advanced HVAC systems, utilized higher performing thermal insulation, and phase change materials for thermal storage all of which requires significant financial investment, as described in articles by Sadineni, S. B.; Madala, S.; Boehm, R. F.: Passive Building Energy Savings: A Review of Building Envelope Components in journal Renewable Sustainable Energy Reviews, 2011, 15, 3617-3631; by Wang, S.; Ma, Z. in Supervisory and Optimal Control of Building HVAC Systems: A Review, HVAC&R Research, 2008, 14, 3-32; by Memon, S. A. in Phase Change Materials Integrated in Building Walls: A State of the Art Review in journal Renewable Sustainable Energy Reviews, 2014, 31, 870-906. Instead, personal thermal comfort technologies offer a potentially low cost solution towards mitigating energy use by HVAC systems. Although these technologies can be used in a variety of indoor and outdoor environments, the focus of this work is to provide personal cooling in temperature regulated indoor environments.
At present, several technologies are commercially available which provide varying degrees of personal cooling. However, these technologies are typically tailored as high performance products, such as sportswear, body armor, and personal protection equipment, thus limiting functionality for everyday use. Arguably the most prevalent personal comfort technology used in industry today is moisture wicking where sensible perspiration is drawn away from the skin to the outer surface of the fabric and evaporated to ambient air thus cooling the wearer passively, as described in Hong, C. J.; Kim, J. B. A Study of Comfort Performance in Cotton and Polyester Blended Fabrics. I. Vertical Wicking Behavior. Fibers Polymer. 2007, 8, 218-224; Kaplan, S.; Okur, A. Thermal Comfort Performance of Sports Garments with Objective and Subjective Measurements, Indian Journal of Fibre & Textile Research, 2012, 37, 46-54; and Das, B.; Das, A.; Kothari, V. K.; Fanguiero, R.; de Araújo, M. Effect of Fibre Diameter and Cross-Sectional Shape on Moisture Transmission through Fabrics, Fibers and Polymer. 2008, 9, 225-231. The drawback of this technology is that it is activated only when the wearer is sufficiently perspiring so that moisture accumulates on the skin; thus, moisture wicking is not suitable to provide cooling for sedentary individuals. Other technologies utilize phase change materials in the form of cold packs which can effectively draw heat from the human body due to the high latent heat of melting associated with water and other refrigerants as described in, for example McCullough, E. A.; Eckels, S. Evaluation of Personal Cooling Systems for Soldiers, 13th International Society of Environmental Ergonomics Conference, Boston, Mass., USA, 2009; pp. 200-204; Gao, C.; Kuklane, K.; Wang, F.; Holmér, I. Personal Cooling with Phase Change Materials to Improve Thermal Comfort from a Heat Wave Perspective. Indoor Ai 2012, 22, 523-530; Muir, I. H.; Bishop, P. A.; Ray, P. Effects of a Novel Ice-Cooling Technique on Work in Protective Clothing at 28C, 23C, and 18C WBGTs, American Industrial Hygiene Association Journal, 1999, 60, 96-104; and Rothmaier, M.; Weder, M.; Meyer-Heim, A.; Kesselring, J. Design and Performance Cooling Garments Based on Three-Layer Laminates, Medical & Biological Engineering & Computing, 2008, 46, 825-832. However this technology tends to be bulky in size and requires frequent replacement of the cold packs over time rendering this technology inconvenient and expensive to the end user. And finally, several technologies provide active cooling through use portable air conditioning units or liquid cooling, for example as described in Elbel, S.; Bowers, C. D.; Zhao, H.; Park, S.; Hrnjak, P. S. Development of Microclimate Cooling Systems for Increased Thermal Comfort of Individuals. International Refrigeration and Air Conditioning Conference; 2012; p. 1183; Kayacan, O.; Kurbak, A. Effect of Garment Design on Liquid Cooling Garments, Textile Research Journal, 2010, 80, 1442-1455; Yang, J.-H.; Kato, S.; Seok, H.-T. Measurement of Airflow around the Human Body with Wide-Cover Type Personal Air-Conditioning with PIV, Indoor and Built Environment, 2009, 18, 301-312; Yang, Y.-F.; Stapleton, J.; Diagne, B. T.; Kenny, G. P.; Lan, C. Q. Man-Portable Personal Cooling Garment Based on Vacuum Desiccant Cooling. Applied Thermal Engineering, 2012, 47, 18-24; and Nag, P. K.; Pradhan, C. K.; Nag, A.; Ashetekar, S. P.; Desai, H. Efficacy of a Water-Cooled Garment for Auxiliary Body Cooling in Heat, Ergonomics 1998, 41, 179-187. These systems not only consume power, but also tend to be prohibitively expensive.